Shelf unit



FIG. 1 is a perspective view of a shelf unit showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a left side view thereof, the opposite side being a mirror image of the side shown; and,

FIG. 5 is a rear elevational view thereof. 

The ornamental design for a shelf unit, as shown and described. 